Misfire or Clutch?

ak

ak

Legendary Member
Joined
17 April 2000
Messages
2,787
Location
Northern VA
Hi Guys

Well, ever since I got my car back from a shop, my car has been acting weird. When at full throttle, my car sometimes hesitates intermittently throughout the revband. Sometimes it hesitates from 5k-6krpm then pick up the acceleration back. I'm thinking it's the clutch but the problem is very sporadic and inconsistent. In my other cars, when clutch slips, it just wouldn't pick up anything over certain RPM so I'm a little confused. I thought maybe I am getting misfires but I don't think that's it since the engine doesn't seem to hesitate.

My car is 94 with 47k miles. I think it's still on the original clutch. Any insight?
 
Are you seeing your revs falling, or are the revs staying high, but the power is not reaching the wheels for a while? If the latter is the case, I would suspect your clutch. On the other hand, if the revs themselves are dropping, then your engine isn't putting out power, so I would suspect your electrical or fuel systems.
 
Originally posted by Kirthasa:
Are you seeing your revs falling, or are the revs staying high, but the power is not reaching the wheels for a while? If the latter is the case, I would suspect your clutch. On the other hand, if the revs themselves are dropping, then your engine isn't putting out power, so I would suspect your electrical or fuel systems.
Click to expand...

Or the TCS.
 
The rev stays up. I checked my coil earlier this year when I replaced my plugs and they were all within the acceptable range. I turned off TCS while driving hard and it has the same result.

btw, I think my VIN ends with 44
 
Originally posted by ak:
I think they replaced the fuel filter when I did my 60k service several month ago. Fuel pump....i dunno??
Click to expand...

Fuel pumps tend to hold up pretty good, unless you start going FI, or NOS... then youll need more fuel depending on setup...

there are tests you can perform in the manual that will help weed out the fuel issue if you want to pursue this.

tests for pump, filter, regulator.... everything.....
 
Originally posted by PettittsAuto:
Sounds like it could be water in the spark plug holes causing a missfire at times. Did the repair shop clean your motor? Water can get into the spark plug holes especially in the rear. Or it sounds like you may just have a bad coil. Good luck.

Bruce, www.pettittsauto.com

Click to expand...

I did find water in the rear part of where the coils are a while ago. I cleaned it and sealed it tight by changing the cover from front to rear(the gasket was better on the front). I checked yesterday and there was no sign of water. I guess I'll check the coils to be on the safe side...
 
Well, I checked the rear coils today and sure enough, the middle coil and the spark plug were drenched in nasty water. I'm not sure how it got in there because the rear engine bay was completely dry, but then I did drive in the rain. Also, since I have aftermarket header/exhaust, I no longer have some of the heat shields which may have contributed this water coming in
frown.gif


Anyway, I cleaned the plug and the coil and went out to test drive. Here's the weird part though. The car was doing the exact same thing...still hesitation in the mid range. And then as I was about to go back home after about 30-40 min of hard driving, the problem cleared. Skeptically, I went around buzzing again, and this time, no problem. Smooth all the way. This is completely weird and I'd have to monitor it for a while to be sure it's fixed. Thank god it's fixed though...I was battling with the coils in below freezing weather!(no garage right now
redface.gif
)

But in any case, I'd like to thank all of you who contributed. I love this forum!

-ak
 
My car (1991) would exhibit this behavior both times I've had a bad O2 sensor. However, it didn't always throw a check engine light.

Mine usually did it in the in 2-4k RPM range in 4th gear going uphill.... Basically when I floored it when it was under load and out of its powerband. It would hesitate when I first stepped on it, and then after about a half to full second, it would pull normally. When it was doing this, using extend partial throttle with some load (uphill) in the same rpm range would often get it to throw the (front/rear) fuel system code.

-Mike
 
Originally posted by grippgoat:
My car (1991) would exhibit this behavior both times I've had a bad O2 sensor. However, it didn't always throw a check engine light.

Mine usually did it in the in 2-4k RPM range in 4th gear going uphill.... Basically when I floored it when it was under load and out of its powerband. It would hesitate when I first stepped on it, and then after about a half to full second, it would pull normally. When it was doing this, using extend partial throttle with some load (uphill) in the same rpm range would often get it to throw the (front/rear) fuel system code.

-Mike
Click to expand...

Actually, it seems that the 2k-4k rpm problem you speak of exist on my car also. No more hesitation between 4k-6k tho. So it could be that I had two separate problems at the same time.....hmmm??
 
ak, I just re-read your last post again, and the intermittence of the problem also rings a bell with me, too. I think I had the problem intermittently for a few months before it finally became consistent and started throwing the fuel system code. Then I had the O2 sensor replaced, and it went away.

What headers do you have? I have DC Sports headers, but I don't remember if my first instance of this problem was before or after I had the headers installed.

If you've got an extension cable for your O2 sensors (I know this is standard for DC Sports, but I don't know about comptech, RM, etc), it's possible you could have an intermittent connection.

My mechanic, when I had one of the O2 sensor replaced (don't remember which one or when), also made some simple brackets for me to keep the O2 sensor wires well under control.

I'm also wondering if, since the DC Sports headers place the O2 sensor bungs under the car, and I drove in a lot of rain, if that took a toll on my O2 sensors. I'm hoping it was just old sensors finally giving up the ghost.

-Mike
 
Also, on the coil cover, I'm pretty sure there's only a gasket on one side of the cover, and I'm also pretty sure that the gasket is supposed to go up (toward the middle of the motor).

Another note: whenever I had the hesitation problem, it would always clear up when the check engine light came on (probably because it switched to a default fuel map).

Another interesting note: When my car dynoed 268 rwhp, it had a bad O2 sensor, and I think the check engine light was on when I made that particular run.

-Mike
 
Hey Mike..Interesting... I have Comptech Header and it did come with cable extention. I definitely didn't have this issue before the header. Next time I go to oil change, i'll tell them to check the wire. I haven't gotten CEL to come on yet.

When you replaced your O2 sensor, did you replace both of them??
 
I only replaced one at a time. And I'm not entirely sure that it was one front and one rear. I'd have to dig up my records to double-check. I'm gonna guess it was probably about a year apart that I had them replaced. The second one went bad sometime turing my 8000-mile road-trip (including 2 days at Road America) for NSXpo 2001.

-Mike
 

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